Alignment 101

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					   Pre-alignment: How
15 Minutes Can Save You
       Stan Riddle
What is coupling alignment?

                  Coupling alignment
                   is shaft alignment. If
                   the shafts are
                   aligned, the
                   couplings will
                   normally go along for
                   the ride.
Types of Couplings

     Rigid – usually must        Flexible – uses one
      be aligned to very           or more elements to
      close tolerances.            connect the shafts.
      Think of it as solidly         Mechanical
      bolting one shaft to           Elastomeric
                                     Metallic
                                    These can tolerate
                                      slightly more
                                      thermal changes,
                                      and shock.
Shaft Alignment
Every shaft, bent or straight, rotates
about an axis that forms a straight

Shafts in this same straight line are
considered co-linear, or in the same
            straight line.
                  Types of Misalignment

Offset, or Parallel – the       Angular – the shafts are not in
shafts are parallel to each     the same plane, which causes
other, but are not co-          a difference in measurement
planar, or in the same          between measurements made
plane. This can be both         180 degrees opposite on the
vertical and horizontal.        coupling faces.

     It’s almost always a combination of both!
         Measurement Conventions

   Offset or Parallel
    Misalignment is
    measured in
    thousandths of an
    inch (0.000”), also
    called mils.
   Angular Misalignment
    is measured in
    thousandths of an
    inch (0.000”), or mils,
    per inch of coupling
Pre-alignment Steps

15 minutes or so of preparation time can save
 you hours, and dollars, in alignment costs.
It can also save you a lot of unnecessary work
  The following slides list some of the most
common errors made both before, and during,
              shaft alignment.
Error #1

   Don’t assume it’s aligned correctly, even if you did it the last time.
   Can the shafts be rotated together? Can they be rotated
    individually? You may have to modify your alignment technique.
   Is there a soft foot issue? Check and minimize before alignment.
   Is there going to be thermal growth? How much? Which
    direction? Is it going to get hotter, or colder?
   Is the coupling insert worn? Does it need replacement?
   Is there adequate spacing between the shafts? Between
   Has pipe strain been minimized?
   Is the pump assembly sitting on isolators? Are they functioning
   Is the pump assembly sitting on an inertia block? Is it properly
    affixed to the floor?
   Do you notice any cracks in the floor around the base? Can
    you feel vibration in the floor?
   Does the coupling insert have excessive backlash?
   Are the coupling flanges tight to the shaft?
   Are set screws and bolts tight?
   Are keys in place?
   Are the hubs concentric? You may be able to align an
    eccentric hub, but may cause vibration, and make you look
    bad, if you miss it.
   Does the coupling guard clear the coupling?
   How clean is the area?
   Soft foot is not limited to just under the motor feet. It can
    happen between a riser and frame, and between a frame and a
   Are there jackbolts? Are they screwed tight to the motor?
 Error #2

You do not know what your
   alignment target, or
       tolerance, is.
Alignment Targets

     Does your company have an alignment
      criteria, or tolerance?
        The coupling manufacturer’s tolerance
         is based upon the amount of
         misalignment the coupling will tolerate,
        NOT what the bearings and seals will
     Think of it like a rubber band…
Alignment Tolerances
                        Alignment tolerances are based on
                        many things, including:
                        •Coupling type
                        •Running speed
                        •Company guidelines
                        Most alignment tool manufacturer’s
                        also have tolerances. Consult your
                        Engineering department, or your
VibrAlign’s tolerance   alignment tool representative, for
                        more information.
  Thermal Growth Targets

Machines that operate at a considerably hotter
or colder condition than the ambient room
temperature should be thermally compensated.

   They will “grow” or
“shrink” as they heat up, or
          cool off
The machine manufacturer’s specs are a good place to start

  But, the machine manufacturer probably does not know:

•The exact temperature of the driver and driven machines
•Ventilation quality or cooling effects
•Piping strain influences
•Piping thermal changes
Coefficient of Thermal Expansion

                     If you can’t
                     remember this
                     chart, remember

                     1foot of steel get 100
                     degrees hotter, it grows
                     about 8 mils ( 0.008”)
However, this is not a magic formula!

   Machines do not usually heat or cool at the
    exact same temperature top to bottom.
   You need to find a mean, or average
    temperature of the machine – from the
    centerline of the shaft, to the bottom of the foot.
The Best Way to Know Thermal Growth Changes…

       …is to measure them yourself.
       Measure the machine in the cold condition, and
        pre-set it to the manufacturer’s
       Re-measure in the hot condition, if possible.
       Some lasers can do this calculation for you, or
        you can simply plot it on paper.
       In addition, some laser alignment tool
        manufacturers sell equipment that allow you to
        measure the thermal changes.
Error #3
Not correcting for soft foot
   Soft foot…

    Soft foot occurs when machine    Soft foot is caused by deformed machine
    feet do not rest flatly on the   base plates or by deformed machine feet.
    machine base.

  Soft foot can be offset, angular, or both.
Error #4 – Not knowing when to say when

     When the machine is aligned to within your
      alignment tolerance, you are done.
     Don’t try to get it all the way to zero.
     You may cause more problems than you
     AND, you will certainly waste time.
Error #5 – Not roughing in

  Straightedge, flashlight, feeler gauges,
    taper gauge, outside caliper, etc…
A Quick Comment on Shims…
     Try to use a maximum of 4 or less shims under each
      foot. It’s not always possible, but try to minimize the
      number of shims per foot.
     Use pre-cut stainless steel shims.
     You can’t cut them for less than you can buy them.
     When you insert shims under the foot, slide them all
      the way in, then back them out ¼”, so the bolt threads
      don’t bend them.
     Don’t reuse painted, or badly bent shims.
     Be careful. A 0.003” shim can cut you like a knife.
      Trust me on this one!
     Keep them neat.
Error #6 Not controlling backlash or unwanted movement

      Some alignment systems are sensitive
       to backlash or “play” in the coupling.
       Not only lasers, but indicators can be
       misread due to backlash, especially if
       there is any eccentricity in the coupling.
      Beware of bumping your indicators or
       laser detectors.
      Beware of any binding or tightness in
       the machines as they are rotated.
Error #7 – Incorrect sequence of moves

      Always correct vertical misalignment
      Once the vertical (top to bottom, up and
       down) is corrected, you can
       theoretically move the machine side to
       side as far as it will go, without
       changing the vertical alignment.
      Then, correct misalignment in the
       horizontal plane (side to side).
Now we’re ready to align!
You got to make the right
Regardless of the method
you use, alignment needs
 to be done in four steps
Angular misalignment in the Vertical Plane

            Side View
Parallel Offset in the Vertical Plane

          Side View
Angular misalignment in the Horizontal Plane

                Top View
Parallel Offset in the Horizontal Plane

             Top View
So what do we do if it doesn’t?
    Check for soft foot.
    Check for bolt or base bound condition.
    Check to make sure you haven’t
     bumped or moved your alignment tools
    Check for coupling backlash.
    Check for excessive vibration in the
    Re-measure, and see if your results are
           Stan’s Tricks of the Trade
   A straightedge, an outside caliper, a Starrett taper gauge,
    and a flashlight are good roughing-in tools.
   A can of compressed air, like those used for cleaning
    electronics, is good to clean dirt out from under motor
   A 0-1” micrometer is great for measuring the thickness of
    shim stacks.
   When aligning, excessive backlash can be compensated
    with a few rounds of duct tape.
   Two dial indicator magnetic bases make great stops to
    rest the laser tool or indicator brackets at the 3 and 9
    o’clock positions. It gives you an extra set of hands.

             Stan Riddle

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